If the Hibiscus is in a pot you will need to re-pot it in fresh soil and spray it down with horticultural oil. If it is a perennial and in the ground just keep on spraying the under and over sides of the leaves.

Talk to professionals FIRST at an independent garden store in your area. they are not dummies hired to fill a position like a big box store. Those people have no clue. They will tell you what to use on your plant. Don't trust home remedies from people. Get professional help they know how to treat those bugs. They are a mess to deal with. We tried for several years. Cut it down, poured gas on the stump of our snowball bush that the aphids were eating to death. The aphids went in the garbage, Gasoline went on the stump and roots. Ah, we finally killed it. The next spring, it showed a little green and started growing. The other night, we saw a bloom of a white snowball. Don't ask me to explain what happened. Maybe the bugs wanted diesel not unleaded regular.